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Schottky contact

Posted 02.12.2009, 21:44 GMT-5 1 Reply

Yuanzhao Yao
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I read the Semiconductor Device section in Model Library, and I wonder the boundary conditions at Metal-Semiconductor contact in devices. From my understanding, the boundary conditions used in the semiconductor device model are only for Ohmic contact. For the case of Schottky contact, the charge at the contact is not zero, could COMSOL also deal with this kind of contact and what kind of modification is needed for it?
To describe a single Schottky contact with applied voltage, the depletion region edge is always used as a boundary condition, but with increasing voltage, the depletion region shrink. For this moving boundary conditon, how could I deal with it, using ALE?

Thank you in advance.
1 Reply Last Post 26.03.2010, 04:07 GMT-4
COMSOL Moderator

Hello Yuanzhao Yao

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Oliver Ottinger
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Posted: 1 decade ago 26.03.2010, 04:07 GMT-4
Dear Yuanzhao,

The used boundaries in the example are not Ohmic in the way that the field disappears at the contact. But nevertheless the charge density does not change with voltage. For a Schottky contact a field dependent injection barrier exists. Where the barrier is changed with a term proportional to sqrt(field).
I do also work on such a problem.
The problem I do see is the implementation of the boundaries. Since the charge density now depend on the field. This means there are to ways:
implement the field(charge density) or charge density(field).

I'm not sure which is the better one. The second has the disadvantage that the field as derivative of the potential is used for the definition of the density - which seems to be less accurate.

Do you know which is the best way?

Concerning the meshing I would prefer to stay at one length scale and normalize the length to the depletion region.

Best regards,
Oliver
Dear Yuanzhao, The used boundaries in the example are not Ohmic in the way that the field disappears at the contact. But nevertheless the charge density does not change with voltage. For a Schottky contact a field dependent injection barrier exists. Where the barrier is changed with a term proportional to sqrt(field). I do also work on such a problem. The problem I do see is the implementation of the boundaries. Since the charge density now depend on the field. This means there are to ways: implement the field(charge density) or charge density(field). I'm not sure which is the better one. The second has the disadvantage that the field as derivative of the potential is used for the definition of the density - which seems to be less accurate. Do you know which is the best way? Concerning the meshing I would prefer to stay at one length scale and normalize the length to the depletion region. Best regards, Oliver

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